Interaction DiagramsCurt Clifton

Rose-Hulman Institute of Technology

Anonymous Feedback“ There is not enough information in the partial use cases, scope and requirements to go into the type of depth an operational contract with any type of certainty. This is taking too much time having to “come up” with details that should have already been laid out by the requirements document and easily accessible.”

OCs are part of the requirements

You have the domain model, which is most pertinent

This course is all about dealing with uncertainty and resolving it

You won’t be penalized for answers that are different than mine so long as they follow the guidelines

What Matters Most?

Principles of assigning responsibilities to objects

Design patterns

But we need some notation

to communicate these ideas

Interaction Diagrams

For dynamic object modeling

Two common types:

Sequence diagrams

Communication diagrams

Don’t confuse with System Sequence Diagrams (SSDs),

which use a subset of the notation

Q1,2

Sequence DiagramExample

public class A { private B myB = new B(); public void doOne() { myB.doTwo(); myB.doThree(); }}

Communication Diagram Example

public class A { private B myB = new B(); public void doOne() { myB.doTwo(); myB.doThree(); }}

Relative Strengths

Sequence diagrams

Clearer notation and semantics

Better tool support

Easier to follow

Excellent for documents

Communication diagrams

Much more space efficient

Easier to modify quickly

Excellent for UML as sketch

Why Bother with Interaction Diagrams?

Keep us from getting bogged down in syntax

Can allocate responsibilities with minimal commitment

But don’t get bogged down

Common Notation

Lifeline Boxes

Q3

Message Syntax

id = message(parameter : parameterType) : returnType

Much is optional, for example:

initialize(register)initialized = getProductDescription(id)d = getProductDescription(id:ItemID)d = getProductDescription(id:ItemID) : ProductDesc

Sequence Diagrams

:Register :SaledoX

doA

doB

doC

doD

Terminology

Found message

Execution specification bars

Synchronous messages

Q4

Two Ways of Illustrating Return Values

Messages to Self

Instance Creation conventional message name

Note dashed line!

Instance Destruction

“stereotype”

Cartoon of the Day

General solutions get you a 50% tip

http

://x

kcd.

com

/287

/

Speaking of Sales…Recall Interaction Frames

Frame operator

Guard

Common Frame Operators

Operator Meaning

alt

loop

opt

par

region

ref

sd

“alternative”, if-then-else or switch

loop while guard is true, or loop(n) times

optional fragment executes if guard is true

parallel fragments

critical region (single threaded)

a “call” to another sequence diagram

a sequence diagram that can be “called”

Mutual Exclusion “alt” Frame

Divides sections of frame Q5

Iterating Over a Collection—Version 1

Action box contains arbitrary statements from implementation language

One instance from a collection

Iterating Over a Collection—Version 2

Leaves the loop implicit.

Abstracting Interaction

Interaction occurrence ref frames

sd framesQ6

:GameStarter :Game

:ClockstartGame

create

run

beginPlay

Asynchronous Calls

Asynchronous (non-blocking) call

Synchronous (blocking) call

Q7

Active object has its own thread

And now for something completely different

Communication Diagrams

Links vs. Messages

Single link connects two objects

Multiple messages

traverse links

Sequence number gives ordering

Q8

Sequence Numbering

No number on found message

Nested messages use “legal” style

Conditional MessagesUse Guards

Q9a

Iteration Uses Stars

Q9b

:GameStarter :Game

:Clock

startGame

1: create

2: run

3: beginPlay

Asynchronous Calls

Asynchronous (non-blocking) call

Synchronous (blocking) call

Q10

Active object